Differential gage



J. B. WILKINSON.

DIFFERENTIAL GAGE.

APPLICATION FILED JULY 5. 1918.

Patented May 18, 1920.

IN {llllllllll Ill/M UNITED STATES PATENT OFFICE.

JOHN B. WILKINSON, 0F MILWAUKEE, WISCONSIN, ASSIGNOR OE ONE-HALF T0 JOHN C. WHITE, OF MADISON, WISCONSIN,

' DIFFERENTIAL GAGE.

Specification of Letters Patent.

Application filed July 5, 1918. Serial No. 243,311

To all whom 2'25 may concern:

Be it known that I, JOHN B. WILKINSON, a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented certain new and useful Improvements in Differential Gages, of which the following is a specificatio This invention relates to gages or meters adapted to indicate pressure difi'erentials induced by fipwing liquids or gases set up or existing between different pressure zones or vessels, and the form of my invention herein disclosed maybe successfully em-.

ployed for indicating the rate of flow of steam through a pipe which supplies an engine or turbine or other steam operating mechanism or apparatus.

One of the primary objects of this invention is the provision of a gage which will be simple in construction, cheap to manufacture, and very durable and extremely accurate in operation without liability to get the tube movement per unit of pressure difference was small and, for the range of dif ferentials encountered, too limited to be of practical use.

My present invention is designed to pro vide a gage in which'- the tendency of each tube to straighten out under the influence of internal pressure exerted thereon is not resisted solely by the material of which the tube is constructed, but is resisted also by the other tube so that the movement of each tube is partially controlled by the other tube with the result that the cooperation between the tubes enables each to be'made of lighter material than would be possible if the tubes did not so cooperate.

For the purpose of facilitating an understanding of my invention, I have illustrated on the accompanying drawings one preferred embodiment thereof from an inspection of which, when considered in connection with the following description, one form ofmy invention and many of its inherent advantages should be readily appreciatedand understood.

Referring to the drawings, Figure 1 is a face View of my improved gage with the front cover largely broken away to clearly show the interior parts. Fig. 2 is a medial vertical sectional view through the gage shown in Fig. 1, and Fig. 3 is a perspective view with the front plate removed, showing the manner of attachment ofmy improved gage to a fluid supply pipe.

Referring to the drawings, reference character 5 indicates generally the instrument casing comprising the back and circumferential walls as clearly shown, Within the casing and upon opposite sides thereof, I have fixedly mounted upon hollow bosses 6.

.and 7 a pair of Bourdon tubes 8 and 9, re-

spectively. These tubes are in communication at their fixed ends with coupling members 11 and 12 projecting outside the casing through whichthe instrument is connected up by suitable piping as will belater explained.

It will be observed that the two tubes 8 and 9 are oppositely disposed so that their free ends normally lie in over-lapping relation and these ends are provided with projecting solid portions 13 and 14:, respectively, which are pivotally connected togetlier by pivot pin 15. It will thus be manifest that any movement of either tube causes a corresponding but reverse movement of the other tube so that when one tube tends to straighten out this tendency is somewhat resisted or counteracted by the ingreased curvature imposed upon the other tu e.

In order that the movements of the connected free ends of these tubes may be utilized to indicate pressure differentials in the tubes, I have provided a simple indicating mechzanism comprising a pointer 16 pivoted at 1 from the rear wall of the casing, this pointer being connected by link 18 with a lever 19, which is pivoted at 21 to a pintle 22 also fixed to the rear wall of the casing. The pivot pin 15 serves notonly to connect the free ends of the tubes 8 and 9 but also connects these tubes to the lever 19 upon a pintle extending forwardly intermediate its ends so that this lever will partake of any movements of the tubes, and these movements will be transmitted through the link 18 to the pointer 16, causing its free end to travel over the face of a dial or scale 23 mounted upon the rear wall of the casing as shown in Fig. 2. The mechanism above described is inclosed within the casing and protected by front cover plate 24 which is provided opposite the dial 23 with a sight opening 25 covered by a glass or other transparent plate 26 through which the position of the pointer 16, with respect to the scale, may be observed.

One manner of connecting up my instrument is shown in Fig. 3 in which reference character 27 indicates a fluid supply pipe through which steam or other fluid is conducted to a point of use. lVithin this pipe I have arranged a stricture in the form of a Venturi tube '28, the throat of which is provided with a series of apertures 29 through which communication is established between the interior of the tube and the chamber 31 surrounding the tube. hen the fluid is flowing under pressure through the pipe the change from static to velocity head as the fluid passes through the throat of the tube causes a reduction of pressure at this point and, consequently, in the chamber 31 so that a differential of pressure, depending upon the rate of flow, exists between the chamber 31 and the intake end of the venturi. In order to subject the differential of pressure thus obtained to a reading by means of my gage above described, I connect the chamber 31 with the connection 12 of the instrument through a pipe 32 and connect the pipe 27 above the intake end of the venturi with the connection 11 by means of a pipe 33. The pressures existing in the pipe 27 at the points of connection of the pipes 32 and 33 therewith are thereby transmitted to the tubes 9 and 8, respectively, thus causing this pressure differential to be indicated by the pointer 16.

After the instrument has been connected up as above explained and the flow of fluid through the pipe 27 has been established, the increased pressure exertedinteriorlyupon the tube 8 will cause this tube to tend to straighten out. The pressure exerted upon the tube!) will also cause this tube to tend to straighten out, and if the pressures are equal no movement of the tubes will take place and the pointer 16 will remain at I its normal zero indication. If, however, the pressure in the tube 8 is greater than the pressure in the tube 9, as customarily is the case, the free end of the tube 8 will move toward the right, viewing Fig. 1, carrying with it the free end of the tube 9 and also the lever 19. The extent of this movement will of course be determined by the diflerences in pressure in tubes 8 and 9, and when a movement sufficient to balance the tubes has taken place, the tubes will remain quiescent and the pointer 16 will indicate on the scale the pressure differential existing in the tubes. It is understood, of course, that under no pressure or under pressures of equal amounts exerted in the tubes the pointer will stand at zero on the scale.

It is believed that one form of my invention and its method of operation will be fully understood from the foregoing without further description, but it should be manifest that various changes in the size, shape, proportion and arrangement of the various parts may be resorted to without departing from the spirit of the invention as set forth in the following claims.

I claim:

1. A differential gage, comprising a case, a pair of Bourdon tubes fixedly mounted at one end at opposite sides of said case and pivotally connected together at their other ends by a common pivot pin, said tubes being arranged with their longitudinal axes in a common plane, a lever attached to said pin, a pivoted pointer, and a link connecting said lever and pointer whereby movement of said tubes induced by differential pressures therein is indicated by said pointer.

2. A differential gage, comprising a case, a pair of Bourdon tubes connected at one end to opposite sides of said case, said tubes being disposed with their longitudinal axes in a common plane, a pivotally mounted lever, a pin connecting said lever and the free ends of said tubes, a pointer and a connection between said lever and said pointer.

3. A differential gage, comprising a case, a pair of Bourdon tubes mounted at opposite sides of said case with their free ends in contiguous relation, a lever, a pivot pin connecting said lever and said free ends of the tubes, a pivoted pointer, and a link connecting said lever and said pointer.

JOHN B. WILKINSON. 

